Platinum supported on pristine and nitrogen-doped bowl-like broken hollow carbon spheres as oxygen reduction reaction catalysts

Mashindi, Victor; Mente, Pumza; Mpofu, Nobuhle; Coville, Neil J.; Makgae, Ofentse A.; Kirkland, Angus I.; Forbes, Roy P.; Ozoemena, Kenneth I.; Levecque, Pieter

doi:10.1007/s10800-021-01554-0

Cited by 14 publications

(10 citation statements)

References 58 publications

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“…Also, in these shell regions of the supports, the Pt maps indicate more than a single layer of Pt particles, indicating penetration into the HCSs/NHCSs shells by the Pt particles as it occupies the pores of the support. This is in agreement with studies on broken hemispherical carbon that were similarly prepared ( Mashindi et al, 2021 ).…”

Section: Resultssupporting

confidence: 91%

“…The higher loss in activity of the benchmark Pt/C is ascribed to low pore confinement compared to the new materials. Pore confinement of the Pt in the structure of the HCSs based supports was confirmed in a similar study involving broken hemispherical hollow carbon spheres (Mashindi et al, 2021).…”

Section: Support Durabilitymentioning

confidence: 56%

“…The TGA and DTGA profiles of Pt/HCSs and Pt/NHCSs recorded the residual PtO/PtO 2 species with Pt content >35 wt.% similar to the nominal 40 wt.% of both the Pt/HCSs and Pt/NHCSs catalysts. The deposition of Pt nanoparticles enhanced the combustion of the carbon, through the expected catalytic reaction of carbon with Pt(Mashindi et al, 2021) and consequently lowered the thermal stability of the materials as shown by the lower decomposition temperatures of the Pt/HCSs The decomposition of Pt/NHCSs also occurred at a lower temperature compared to the NHCSs, in agreement with the presence of defects on the NHCSs, as shown by Raman spectroscopy.…”

mentioning

confidence: 65%

“…40 wt.% loading) and compare the data to a commercial benchmark Pt/C catalyst (Yano et al, 2010;Lu et al, 2013;Lee et al, 2014). The work continues from an earlier paper that investigated placing Pt on broken HCSs (Mashindi et al, 2021). The load cycling and startstop durability of these materials were investigated and the changes in activity and electrochemical surface area were measured and correlated with the durability data.…”

Section: Introductionmentioning

confidence: 96%

“…Currently, the state-of-the-art PEMFC catalyst is a Pt or a Pt/transition metal bimetallic catalyst placed on a variety of supports. Supports that have been used vary from structured carbons like nanotubes (CNTs), nanofibers (CNFs), carbon black (CB), broken hemispherical hollow carbons (BHCSs) as well as doped metal oxides and carbides ( Mao et al, 2019 ; Jiménez-Morales et al, 2020 ; Mohideen et al, 2020 ; Wang et al, 2020 ; Mashindi et al, 2021 ). Carbon supports are favoured due to their different structured forms, their lightweight that is important for mobile applications, thermal stability for high-temperature applications, high surface area for nanoparticle deposition and gas diffusion, as well as their earth abundance.…”

Section: Introductionmentioning

confidence: 99%

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Platinum Nanocatalysts Supported on Defective Hollow Carbon Spheres: Oxygen Reduction Reaction Durability Studies

et al. 2022

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The durability and long-term applicability of catalysts are critical parameters for the commercialization and adoption of fuel cells. Even though a few studies have been conducted on hollow carbon spheres (HCSs) as supports for Pt in oxygen reduction reactions (ORR) catalysis, in-depth durability studies have not been conducted thus far. In this study, Pt/HCSs and Pt/nitrogen-doped HCSs (Pt/NHCSs) were prepared using a reflux deposition technique. Small Pt particles were formed with deposition on the outside of the shell and inside the pores of the shell. The new catalysts demonstrated high activity (>380 μA cm−2 and 240 mA g−1) surpassing the commercial Pt/C by more than 10%. The catalysts demonstrated excellent durability compared to a commercial Pt/C in load cycling, experiencing less than 50% changes in the mass-specific activity (MA) and surface area-specific activity (SA). In stop-start durability cycling, the new materials demonstrated high stability with more than 50% retention of electrochemical active surface areas (ECSAs). The results can be rationalised by the high BET surface areas coupled with an array of meso and micropores that led to Pt confinement. Further, pair distribution function (PDF) analysis of the catalysts confirmed that the nitrogen and oxygen functional groups, as well as the shell curvature/roughness provided defects and nucleation sites for the deposition of the small Pt nanoparticles. The balance between graphitic and diamond-like carbon was critical for the electronic conductivity and to provide strong Pt-support anchoring.

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Section: Resultssupporting

confidence: 91%

Section: Support Durabilitymentioning

confidence: 56%

mentioning

confidence: 65%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Platinum Nanocatalysts Supported on Defective Hollow Carbon Spheres: Oxygen Reduction Reaction Durability Studies

et al. 2022

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Monitoring the Morphological Changes of Skeleton‐PtCo Electrocatalyst during PEMFC Start‐Up/Shut‐Down probed by in situ WAXS and SAXS

Janssen,

Drnec,

Martens

et al. 2024

ChemSusChem

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Advanced in situ analyses are indispensable for comprehending the catalyst aging mechanisms of Pt‐based PEM fuel cell cathode materials, particularly during accelerated stress tests (AST). In this study, a combination of in situ small‐angle and wide‐angle X‐ray scattering (SAXS & WAXS) techniques were employed to establish correlations between structural parameters (crystal phase, quantity, and size) of a highly active skeleton‐PtCo (sk‐PtCo) catalyst and their degradation cycles within the potential range of the start‐up/shut‐down (SUSD) conditions. Despite the complex case of the sk‐PtCo catalyst comprising two distinct fcc alloy phases, our complementary techniques enabled in situ monitoring of structural changes in each crystal phase in detail. Remarkably, the in situ WAXS measurements uncovered two primary catalyst aging processes, namely the cobalt depletion (regime I) followed by the crystallite growth via Ostwald ripening and/or particle coalescence (regime II). Additionally, in situ SAXS data reveal a continuous size growth over the AST. The Pt‐enriched shell thickening based on the Co depletion within the first 100 SUSD cycles and particle growth induced by additional potential cycles were also collaborated by ex situ STEM‐EELS. Overall, our work shows a comprehensive aging model for the sk‐PtCo catalyst probed by complementary in situ WAXS and SAXS technique.

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Structurally Tunable Graphitized Mesoporous Carbon for Enhancing the Accessibility and Durability of Cathode Pt‐Based Catalysts for Proton Exchange Membrane Fuel Cells

Wu,

Meng,

Xiong

et al. 2024

Small Science

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Low Pt utilization and intense carbon corrosion of cathode catalysts is a crucial issue for high‐efficiency proton exchange membrane fuel cells due to the highly demanded long‐term durability and less acquisition/application cost. Herein, structurally tunable graphitized mesoporous carbon (GMC) is obtained by direct high‐temperature pyrolysis and in situ‐controlled mesopore formation; the structure‐optimized GMC1300‐1800 exhibits a mesopore size of 7.54 nm and enhanced corrosion resistance. Functionalized GMC1300‐1800 is loaded with small‐sized Pt nanoparticles (NPs) (1.5 nm) uniformly by impregnation method to obtain Pt/GMC1300‐1800 and form an “internal platinum structure” to avoid sulfonic acid groups poisoning as well as ensure O2/proton accessibility. Hence, the electrochemically active surface area (ECSA) of Pt/GMC1300‐1800 reaches 106.1 m2 g−1Pt, while mass activity and specific activity at 0.9 V are 2.1 and 1.4 times those of commercial Pt/C, respectively. Notably, the ECSA decay is less than 17% for both 30 000 cycles’ accelerated durability tests (ADTs) of Pt attenuation and carbon attenuation. Accordingly, the optimized mesoporous structure of GMC1300‐1800 significantly decreases the coverage of sulfonic acid groups on Pt NPs, leading to the highest peak power density in the single‐cell test. Density functional theory calculations demonstrate the synergistic effect between graphitization and mesoporosity on enhancing the accessibility and durability of the catalysts.

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Platinum supported on pristine and nitrogen-doped bowl-like broken hollow carbon spheres as oxygen reduction reaction catalysts

Cited by 14 publications

References 58 publications

Platinum Nanocatalysts Supported on Defective Hollow Carbon Spheres: Oxygen Reduction Reaction Durability Studies

Platinum Nanocatalysts Supported on Defective Hollow Carbon Spheres: Oxygen Reduction Reaction Durability Studies

Monitoring the Morphological Changes of Skeleton‐PtCo Electrocatalyst during PEMFC Start‐Up/Shut‐Down probed by in situ WAXS and SAXS

Structurally Tunable Graphitized Mesoporous Carbon for Enhancing the Accessibility and Durability of Cathode Pt‐Based Catalysts for Proton Exchange Membrane Fuel Cells

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